Recently, there is dramatically growing demand for portable electronic products such as laptop computers, video cameras and mobile phones, and with the extensive development of electric vehicles, accumulators for energy storage, robots and satellites, many studies are being made on high performance secondary batteries that can be recharged repeatedly.
Currently, commercially available secondary batteries include nickel-cadmium batteries, nickel-hydrogen batteries, nickel-zinc batteries, lithium secondary batteries and the like, and among them, lithium secondary batteries are gaining attention due to advantages of charging and discharging freely in the absence of a memory effect, a very low self-discharge rate, and high energy density as compared to nickel-based secondary batteries.
Meanwhile in general, a battery pack includes a plurality of battery modules, each including at least one battery cell, and each battery module is connected in series and/or in parallel within a space provided from the case of the battery pack.
Particularly, to increase the travel distance of elective vehicles such as hybrid electric vehicles, it is inevitable to increase the capacity of the battery pack mounted therein, and as a consequence, the weight of the battery pack amounts to a few hundreds of kilograms.
To minimize the spatial limitation resulting from the seating space of the electric vehicle, the battery pack is often designed such that the battery pack is placed in the battery room provided below the electric vehicle (e.g., below the seats).
Specifically, the case of the battery pack has a plurality of couplers, and each coupler may be fastened through a bolt provided on the side of the lower space of the electric vehicle.
Particularly, when the battery pack is designed such that the battery pack is fixed with a hanging structure on the sides of the battery room provided in the electric vehicle, vibration generated due to the movement of the electric vehicle is transmitted to the plurality of couplers provided in the battery pack through the battery room.
However, conventionally, when performing a vibration test on the battery pack, accuracy in the vibration test results cannot be guaranteed, because the special fixing structure of the battery pack and the electric vehicle described above is not taken into account.